Heat Conduction From an Embedded Component

ABSTRACT

This publication discloses a circuit-board construction and a method for manufacturing an electronic module, in which method at least one component ( 6 ) is embedded inside an insulating-material layer ( 1 ) and contacts ( 14 ) are made to connect the component ( 6 ) electrically to the conductor structures ( 14, 19 ) contained in the electronic module. According to the invention, at least one thermal via ( 22 ), which boosts the conducting of heat away from the component ( 6 ) is manufactured in the insulating-material layer ( 1 ) in the vicinity of the component ( 6 ).

The present invention relates to a method for the manufacture of anelectronic component and a circuit-board construction.

The invention particularly relates to a manufacturing method, in whichone or more components are embedded in an installation base. Theelectronic module being manufactured can be a module like a circuitboard, which contains several components, which are connected to eachother electrically through conductor structures manufactured in theelectronic module. In particular, the invention relates to an electronicmodule, which contains microcircuits, to which several contact terminalsare connected. Of course, in addition to, or instead of microcircuits,other components too, for example passive components, can be embedded inan installation base. The intention is thus to embed in the electronicmodule components that are typically attached uncased to a circuit board(to the surface of the circuit board). Another important component groupconsists of components that are typically encased for attachment to acircuit board. The electronic modules, to which the invention relates,can of course also include other kinds of components.

The installation base can be of a type that is generally used in theelectronics industry as a base for installing electrical components. Thetasks of the base are to provide a mechanical attachment base for thecomponents as well as the necessary electrical connections, both to theother components on the base and to those outside the base. Theinstallation base can be a circuit board, so that the structure andmethod to which the invention relates are closely associated withcircuit-board manufacturing technology. The installation base can alsobe some other base, for example, a base used for packaging a componentor components, or the base of a complete operational module.

Circuit-board manufacturing technology differs from the manufacture ofmicrocircuits, for instance, in that, in the manufacturing techniques ofmicrocircuits, the installation base, that is a substrate, is asemiconductor material, whereas the basic material of the installationbase of circuit boards is some kind of insulation material. Thetechniques for manufacturing microcircuits are also typicallyconsiderably more expensive that those for manufacturing circuit boards.

The casings and packages of components and particularly semiconductorcomponents differ from the construction and manufacture of circuitboards, in that the primary purpose of component packages is to form acasing around the component, which will protect the componentmechanically and facilitate the handling of the component. On thesurface of the component casing, there are connection parts, typicallyprotrusions, with the aid of which the cased component can be easilycorrectly aligned on the circuit board and the desired connectionscreated to it. In addition, there are conductors inside the componentcase, which connect the connection parts protruding outside the case tothe connection areas on the surface of the actual component, throughwhich the component can be connected as desired to its surroundings.

However, the cases of components manufactured using this traditionaltechnology demand a considerable amount of space. As the size ofelectronic devices has diminished, attempts have been made to get rid ofcomponent cases, which not only demand much space, but are alsounnecessary and lead to needless costs. To solve this problem, variousconstructions and methods have been developed, with the aid of whichcomponents can be located inside the circuit-board structure.

Known methods, in which components are embedded in an installation baseduring the creation of the base, are disclosed in patent applicationpublication WO 03/065778 and WO 03/065779, as well as in patentpublications U.S. Pat. No. 6,038,133 and U.S. Pat. No. 6,489,685. Themethods disclosed in these publications can be used to manufacture, forexample, multi-layer circuit boards, inside which integratedmicrocircuits, for example microprocessors and memory circuits, areembedded.

In the known methods, a problem can arise with the heating of themicrocircuits inside the installation base. During operation,microcircuits and particularly certain microprocessors produce asignificant thermal output, which must be conducted away from thecircuit to prevent the circuit from overheating. This is becauseoverheating in a circuit can endanger its reliable operation. Whencircuits are installed, according to the traditional technique, on thesurface of a circuit board, it has been possible to conduct the thermaloutput to the surrounding air, or attach a suitable heat sink to thecircuit. If a circuit is embedded inside a circuit board, the basicmaterial of the circuit-board, which has relatively poor thermalconductivity, will surround the circuit. The thermal output cannot thenbe easily conducted to the surrounding air, nor is it easy to attach aheat sink to the circuit. The thermal output produced by the circuitwill spread from the microcircuit to the surrounding circuit-boardmaterial through direct contact and through the buses connected to thecircuit.

The invention is intended to improve the conducting of the thermaloutput from the embedded components to the surroundings of theinstallation base.

The invention is based on manufacturing at least one thermal viaextending to the vicinity of the component, which will boost theconducting of heat away from the component.

More specifically, the method according to the invention ischaracterized by what is stated in the characterizing portion of Claim1.

The circuit-board structure according to the invention is, in turn,characterized by what is stated in Claim 15.

Considerable advantages are gained with the aid of the invention. Thisis because, with the aid of the invention, it is possible to improve theconducting of the thermal output from a component embedded in aninstallation base to the surroundings of the installation base.Increased conducting of the thermal output will permit the use ofcomponents of greater power than previously inside an electronic-moduleconstruction.

Additional advantages are gained by means of embodiments of theinvention. These embodiments are described in both the followingdescription and in the dependent Claims.

Advantages relating to manufacturing technology can be obtained inembodiments, in which a thermal via, or thermal vias are manufacturedusing the same manufacturing technique as the electrical vias, with theaid of which an electrical contact is created between the contact bumps,or other contact areas of a component and the conductor-pattern layerand the conductor-pattern layers of the circuit-board structure. In suchan embodiment, the manufacture of the thermal vias will not necessarilyrequire any additional stage in the manufacturing method of anelectronic module or other circuit-board construction.

In an embodiment, in which thermal vias are filled with metal with theaid of a chemical and/or electrochemical growing method, the material ofthe thermal vias is pure metal, so that via will have excellent thermalconductivity. When such a via is manufactured in contact with thesurface of the component, excellent thermic contact between the thermalvia and the component will also be achieved.

The embodiment permits the thermal vias to be manufactured precisely inthe desired locations, for example, precisely in the area of thecomponent in which the component's power consumption is greatest.

With the aid of the embodiments, thermal vias can be manufactured in thedirection of both surfaces of the component and even in contact with theside surfaces of the component.

Further, the invention has embodiments that permit suitable dimensionsto be selected for a thermal via. The thermal via can have, for example,a very small cross-sectional area, if there is little space for athermal via. The thermal via can also be large and encompasssubstantially the entire free surface of the component, in which casethe conducting of heat will be very efficient.

In the following, the invention is examined with the aid of examples andwith reference to the accompanying drawings.

FIGS. 1-10 show a series of cross-sections of some examples of theapplication of the invention, in connection with one manufacturingmethod.

FIG. 11 shows a cross-section of one electronic module, which includesseveral installation bases on top of each other, and in which thermalconductors are made around one microcircuit.

STAGE A (FIG. 1)

In stage A, a suitable conductor layer 4 is selected as the startingmaterial for the process. A layered sheet, in which the conductor layer4 is located on the surface of a support base 12, can also be selectedas the starting material. The layered sheet can be manufactured, forexample, by taking a support base 12 suitable for processing andattaching a suitable conductor membrane to the surface of this supportbase 12, for the creation of a conductor layer 4.

The support base 12 can be, for example, of an electrically conductivematerial, such as aluminium (Al), or of an insulating material, such asa polymer. The conductor layer 4 can be created, for example byattaching thin metal foil to one surface of the support base 12, forexample, by laminating it from copper (Cu). The metal foil can beattached to the support base, for example, by using an adhesive layer,which is spread on the surface of the support base 12 or metal foil,prior to the lamination of the metal layer. At this stage, there need beno patterns in the metal foil.

In the example of FIG. 1, holes 3, which penetrate the support base 12and the conductor layer 4, are made in the base, for alignment duringthe installation and connection of the components 6. For example, twothrough-holes 3 can be manufactured for each component 6 to beinstalled. The holes 3 can be made using some suitable method, forexample, mechanically by milling, stamping, drilling, or with the aid ofa laser. However, it is not essential to make through-holes 3, insteadother suitable alignment markings can also be used to align thecomponents. In the embodiments shown in FIG. 1, the through-holes 3 usedto align the components extend through both the support base 12 and theconductor membrane 4. This has the advantage that the same alignmentmarks (through-holes 3) can be used in aligning on both sides of theinstallation base.

Stage A can also be performed in the same way in embodiments, in which aself-supporting conductor layer 4 is used and which thus entirely lackthe support layer 12.

STAGE B (FIG. 2)

In stage B, an adhesive layer 5 is spread on the conductor layer 4, inthe areas to which the components 6 are to be attached. These areas canbe termed connection areas. The adhesive layers 5 can be aligned, forexample, with the aid of through-holes 3. The thickness of the adhesivelayer is selected in such a way that the adhesive completely fills thespace between the component 6 and the conductor layer 4, when thecomponent 6 is pressed onto the adhesive layer 5. If the component 6includes contact protrusions 7, the thickness of the adhesive layer 5should be greater, for example, 1.5-10 times, than the height of thecontact protrusions 7, so that the space between the component 6 and theconductor layer 4 will be well filled. The surface area of the adhesivelayer 5 formed for the component 6 can also be slightly greater than thecorresponding surface area of the component 6, which will also help toreduce the risk of inadequate filling.

The adhesive used in the embodiments is typically a heat-cured epoxy,for example, NCA (non conductive adhesive). The adhesive is selectedsuch that the adhesive used will adhere sufficiently to the conductormembrane, the circuit-board, and the component. One preferred propertyof the adhesive is a suitable thermal expansion coefficient, so thatduring the process the thermal expansion of the adhesive will not differexcessively from the thermal expansion of the surrounding material. Theadhesive selected should also preferably have a short curing time of atmost a few seconds. Within this time, the adhesive should harden atleast partly to an extent that will allow the adhesive to hold thecomponent in place. The final hardening can take a clearly longer timeand indeed the final curing can be planned to occur in connection withthe later process stages. The adhesive should also withstand the processtemperatures used, for example, heating to a temperature of 100-265° C.a few times, as well as other stresses, for example, chemical andmechanical stress, in the manufacturing process. The electricalconductivity of the adhesive should preferably be of the same order asthat of the insulating materials.

Stage B can be modified in such a way that the adhesive layer 5 isspread on the connector surfaces of the components 6, instead of on theconnector areas of the conductor layer 4. This can be performed, forexample, in such a way that the component is dipped in adhesive beforeit is assembled in place in the electronic module. It is also possibleto proceed by spreading the adhesive on both the connector areas of theconductor layer 4 and on the connector surfaces of the components 6.

The adhesive used is thus an electrical insulator, so that electricalcontacts between the contact areas of the components 6 (for example, thecontact protrusions 7) do not arise in the adhesive layer 5 itself.

STAGE C (FIG. 3)

In stage C, the components 6 are set in place in the electronic module.This can be done, for example, by using the aid of an assembly machineto press the components 6 into the adhesive layer 5. In the assemblystage, the through-holes 3 made for alignment, or other availablealignment marks are used to align the component 6.

The components 6 can be glued singly, or in suitable groups. The typicalprocedure is for the conductor layer, which can be referred to as thebottom of the installation base, to be brought to a suitable positionrelative to the assembly machine, after which the component 6 is alignedand pressed onto the bottom of the installation base, which is heldstationary during alignment and attachment.

STAGE D (FIG. 4)

In stage D, an insulating-material layer 1, in which there are readymade holes 2 or recesses for the components 6 glued to the conductorlayer 4, is placed on top of the conductor layer 4. Theinsulating-material layer 1 can be manufactured from a suitable polymerbase, in which holes or recesses, selected according to the size andposition of the components 6, are manufactured using some suitablemethod. The polymer base can be, for example, a pre-preg base, which isknown and widely used in the circuit-board industry, which is made froma glass-fibre mat and so-called b-state epoxy. It is best to performstage D only after the adhesive layer 5 has been cured, or otherwisehardened sufficiently for the components 6 to remain in place while theinsulating-material layer 1 is set in place.

When manufacturing very simple electronic modules, theinsulating-material layer 1 can be attached to the conductor layer 4 inconnection with stage D and the process continued with the patterning ofthe conductor layer 4.

STAGE E (FIG. 5)

In stage E, an unpatterned insulating-material layer 11 is set on top ofthe insulating-material layer 1 and then a conductor layer 9 is set ontop of it. Like the insulating-material layer 1, the insulating-materiallayer 11 can be manufactured from a suitable polymer membrane, forexample, from the aforementioned pre-preg base. The conductor layer 9can be, for example, copper foil, or some other membrane suitable forthe purpose.

STAGE F (FIG. 6)

In stage F, the layers 1, 11, and 9 are pressed with the aid of heat andpressure, in such a way that the polymer (in the layers 1 and 11) formsa unified and tight layer around the components 6 between the conductorlayers 4 and 9. This procedure makes the second conductor layer 9 quiteeven and flat.

When manufacturing simple electronic modules including a singleconductor pattern layer 14, stage E can even be entirely omitted, or thelayers 1 and 11 can be laminated to the structure without the conductorlayer 9.

STAGE G (FIG. 7)

In stage G, the support base 12 is detached or otherwise removed fromthe structure. The removal can take place, for example, mechanically orby etching. Naturally, stage G can be omitted in embodiments in which asupport base 12 is not used.

STAGE H (FIG. 8)

In stage H, holes 17 are made for the vias. The holes 17 are madethrough the conductor layer 4 and the adhesive layer 5, in such a way asto reveal the material of the contact protrusions 7 or correspondingcontact areas of the components 6. The holes 17 can be made, forexample, by drilling with the aid of a laser. The holes 17 can bealigned, for example, with the aid of the holes 3.

At the same time, holes 21 are also made for the thermal vias belongingto the thermal conductors. The holes 21 are made in the same way as theholes 17. If the component 6 includes contact bumps protruding from itssurface, the depth of the holes 21 can correspond to the depth of theholes 17, so that both holes can be made, for example, by applyingexactly the same laser-drilling parameters. The depth of the holes onthe opposite side of the component is, of course, determined by thethickness of the insulating layer on that side. The intention is to makethe holes 21 in such a way that a small amount of insulating materialremains between the bottom of the hole 21 and the component 6, so thatan electrical contact will not be formed between the thermal via and thesurface of the component. A suitable distance can be, for example, 1-15micrometres.

In some embodiments, the thermal vias can also be made up to the surfaceof the component. In that case, the hole 21 too extends to thecomponent. In such embodiments, care must be taken that thesemiconductor material of the component is not connected to the wrongpotential through the thermal via.

If thermal bumps, which are intended to conduct the heat away from thecomponent, have been made on the surface of the component, the holes 21should be attempted to be made at least at the position of such thermalbumps. In that case, the holes 21 can extend to the surface of thethermal bump.

In general, the number, cross-sectional area, and location of thethermal vias are chosen according to the heat-transfer requirement andtaking into account that the thermal conductors must not interfereunnecessarily with the electrical operation of the component. However,it is preferable to locate the thermal vias at, or immediately next tothe component.

In some embodiments, the thermal vias are used to form a ground contactbetween the component and the ground reference plane. In that case, theground contact of the component is made with a considerably largercross-sectional area than normal, or the ground contact is formed fromseveral separate ground contacts, the combined cross-sectional area ofwhich is considerable greater than that of a conventional groundcontact.

STAGE I (FIG. 9)

In stage I, conductor material 18 is grown in the holes 17 and 21 madein stage H. In the example process, the conductor material is grown atthe same time also elsewhere on top of the base, thus increasing thethickness of the insulating layers 4 and 9 too.

The conductor material 18 to be grown can be, for example, copper, orsome other sufficiently electrically conductive material. The selectionof the conductor material 18 takes into account the ability of thematerial to form an electrical contact with the material of the contactprotrusions 7 of the component 6. In one example process, the conductormaterial 18 is mainly copper. The copper metallizing can be performed bydepositing a thin layer of chemical copper in the holes and thencontinuing plating using an electrochemical copper-growing method.Chemical copper is used in the example because it will also form adeposit on top of the adhesive and act as an electrical conductor inelectrochemical plating. The metal can thus be grown using awet-chemical method, so that the growing is cheap.

In the example process, the vias 17 are first of all cleaned using athree-stage desmear process. After this, the vias are metallized, insuch a way that first a polymer catalyzing SnPd coating is formed, afterwhich a thin layer (about 2 μm) of chemical copper is deposited on thesurface. The thickness of the copper is increased by electrochemicaldeposition.

Stage I is intended to form an electrical contact between the component6 and the conductor layer 4 and to fill the holes 21 with a thermallyhighly conductive material. Thus, in stage I it is not essential toincrease the thickness of the conductor layers 4 and 9, but instead theprocess can equally well be designed so that in stage I the holes 17 and21 are only filled with a suitable material. The conductor layer 18 canbe manufactured, for example, by filling the holes 17 with anelectrically conductive paste, or by using some other suitable microviametallizing method. In the case of the holes 21, the filling materialmust conduct heat better than the base material of the circuit board 1.

In the later figures, the conductor layer 18 is shown merged with theconductor layers 4 and 9.

STAGE J (FIG. 10)

In stage J, the desired conductor patterns 14 and 19 are made from theconductor layers 4 and 9 on the surfaces of the base. If in theembodiment only the conductor layer 4 is used, the patterns are formedonly on one side of the base. It is also possible to proceed by formingconductor patterns only from the conductor layer 4, even though a secondconductor layer 9 is used in the embodiment. In such an embodiment, theunpatterned conductor layer 9 can act, for example, as a layer thatsupports or protects the electronic module mechanically, as protectionagainst electromagnetic radiation, or as a surface that conducts thermaloutput outside the module and releases it.

The conductor patterns 14 can be made by removing the conductor materialof the conductor layer 4 from outside the conductor patterns. Theconductor material can be removed, for example, using some of thepatterning and etching methods that are widely used and well known inthe circuit-board industry.

After stage J, the electronics module includes a component 6, or severalcomponents 6, as well as conductor patterns 14 and 19 (in someembodiments, only the conductor patterns 14), with the aid of which thecomponent 6, or components can be connected to an external circuit, orto each other. In addition, the electronic module includes one orseveral thermal vias 22, which extend to the surface of the component 6,or the thermal bump, or to the vicinity of the surface. Thepreconditions then exist for manufacturing an operational totality. Theprocess can thus be designed in such a way that the electronic module isready after stage J and FIG. 10 indeed shows an example of one possibleelectronic module. If desired, the process can also be continued afterstage J, for example, by coating the electronic module with a protectiveagent, or by manufacturing additional conductor pattern layers on thefirst and/or second surface of the electronic module.

FIG. 11

FIG. 11 shows a multi-layer electronic module, which contains threebases 1 laminated on top of each other, together with components 6 and atotal of six conductor pattern layers 14 and 19. The bases 1 areattached to each other with the aid of intermediate layers 32. Theintermediate layer 32 can be, for example, a pre-preg-epoxy layer, whichis laminated between the bases 1. After this, holes penetrating themodule, for the formation of contacts, are drilled in the electronicmodule. The contacts are formed with the aid of a conductor layer 31grown in the holes. With the aid of the conductors 31 running throughthe electronic module, the conductor pattern layers 14 and 19 of thevarious bases 1 can be suitably connected to each other and thus createa multi-layered operational totality. In addition, the conductors 31 canbe used to conduct heat in the vertical direction of the electronicmodule.

In the example of FIG. 11, the power consumption of the component 6′ isgreater than that of the other components and the faultless operation ofthe component 6′ requires boosted conduction of the thermal output fromthe component 6′ to outside the electronic module. In order to conductthe thermal output, thermal vias 22 are manufactured in theaforementioned manner, in the vicinity of the component 6′. The vias 22located in the position shown above the component 6′ extend to close tothe surface of the component 6′ and boost the transfer of heat betweenthe component 6′ and the conductor layer located above it. In thefigure, the direction of the heat conducting is shown by arrows. Theconductor layer acts as a thermal conductor in the lateral direction ofthe electronic module. In addition, the conductor layer is connected tothe vertical thermal conductor 19, with the aid of which the thermaloutput can be conducted from the innermost layers of the electronicmodule to the surface of the electronic module. For their part, thethermal conductors extending to the surface of the electronic module canbe connected to a suitable heat sink, thus further boosting the coolingof the component 6′.

In the position shown in the figure, the via 22 located below thecomponent 6′ also extends to close to the surface of the component 6′and boosts the transfer of heat from the lower surface of the component6′ to the surrounding structures. In this example, the via 22 extends,in the lateral direction of the electronic module, in a direction atright angles to the surface of the figure and conducts heat in thelateral direction away from the vicinity of the component 6′. This heatconducting is shown in the figure by a broken-line arrow.

In the example of FIG. 11, the thermal conductors are manufacturedaround only a single component. The thermal conductors can, however, bemanufactured in a completely similar manner around any other componentwhatever, but in the example of FIG. 11 the other components areimagined to be circuits with a lower power consumption, for whichboosted conducting of the thermal output is not essential. If theconstruction of the electronic module in the surroundings of such alow-power component 6 is compared with that in the surroundings of thehigh-power component 6′, it will be observed that, around the high-powercomponent 6′, the electronic module includes additional structuresemphasized by a pattern of dots. The purpose of these emphasizedstructures is to boost the conducting of heat away from the component6′. The electronic module shown in FIG. 11 differs from known electronicmodules precisely due to these additional structures. Thus, theelectronic module includes conductor structures in the surroundings ofthe embedded component 6′ that are not essential in order to create theelectrical connections of the electronic module and which increase theability of the electronic module to conduct heat away from the component6′. In this example, these thermal conductors are in no way connectedelectrically to the component 6′. In some other embodiments, the thermalconductors, or at least some of them, could, for their part, form, forexample, the ground contact of the component 6′.

Sub-modules of the multi-layer electronic module (the bases 1 with theircomponents 6 and conductors 14 and 19) can be manufactured, for example,using one of the electronic-module manufacturing methods describedabove. Some, or all of the sub-modules to be attached to the layeredstructure can, of course, be manufactured quite as well using some othermethod suitable for the purpose.

The examples of FIGS. 1-11 show some possible processes, with the aid ofwhich our invention can be exploited. However, our invention is notrestricted only to the processes described above, but instead theinvention also covers other various processes and their end products,taking into account the full scope and equivalence interpretation of theClaims. The invention is also not restricted to only the constructionsand methods shown by the examples, but instead it will be obvious to oneversed in the art that the various applications of our invention can beused to manufacture very many different kinds of electronic modules andcircuit-boards, which differ even greatly from the examples describedabove. The components and circuits of the figures are thus shown onlyfor the purpose of illustrating the manufacturing process. Thus manyalterations can be made to the processes of the examples describedabove, without, however, deviating from the basic idea according to theinvention. The changes can relate, for example, to the manufacturingtechniques described in the different stages, or to the mutual order ofthe process stages.

The invention can thus also be applied when embedding components in aninstallation base using other techniques. For example, in connectionwith the method disclosed in the publication WO 03/065778, the thermalvias could be manufactured in the module as surplus holes 12 in stage K(FIG. 1K). In the method of publication WO 03/065779, in turn, surplusholes 13 could be manufactured in stage K (FIG. 1K). The methoddisclosed in U.S. Pat. No. 6,489,685 could, on the other hand, bemodified, for example, in such a way that (references to the examples ofFIG. 2) the thickness of the insulating layer 201 would be increased andvias 204 would also be made at the location of the component 203.Alternatively, the thermal vias could be made after the stage shown byFIG. 2G, according to the example described above that exploits laserdrilling.

In the embodiment shown in FIG. 2 of U.S. Pat. No. 6,038,133, thermalvias could be made, for example, in such a way that thermal bumps aremade in the lower surface of the copper foil 206, which are positionedat the location of the component 204 and which press, in stage g, closeto the surface of the component. In the embodiment of FIG. 3 of the samepatent, thermal vias could be manufactured, for example, in such a waythat an additional conductor area 303 is made on the film 305 betweenthe conductor areas forming a contact to the component. In acorresponding manner, additional conductor areas 306 could bemanufactured in the membrane 307, even though in reality theseadditional conductor areas 306 would, particularly above the component,come to be situated excessively far from the surface of the component.To significantly increase the thermal conduction, it should be possibleto make these additional conductor areas 303 and 306 higher than thethickness of the actual conductors 303 and 306. The thermal conductorswould then be brought closer to the surface of the component.

It is thus possible to also apply our invention in connection with manydifferent kinds of known methods and electronic modules. In addition,the invention can also be applied in connection with the method andelectronic modules disclosed in the same applicant's internationalpatent applications, which are still unpublished at the moment of makingthe present application. For example, in the method disclosed inapplication PCT/FI2004/000195, the invention can be applied in themanner shown in the series of figures shown above.

In the method disclosed in application PCT/FI2004/000101, thermal bumpsmanufactured in the areas between the contact areas of the component.From the other direction, thermal vias could be made, for example, bythe method exploiting laser drilling shown in the series of figuresshown above. Thermal vias above the component can also be made bypressing conductor balls, or other particles that improve thermalconductivity into the filler substance 8, before the filler 8 hardens.It is also possible to proceed similarly in connection with thetechnique disclosed in application PCT/FI2004/000102.

With the aid of the methods described above and variations of them, itis thus possible to manufacture a circuit-board construction, whichincludes an insulating-material layer 1 and at least two conductorpattern layers 14, 19, which are typically on opposite sides of theinsulating-material layer 1. In addition, the circuit-board constructionincludes inside the insulating-material layer 1, at least one component6 and contacts 14, with the aid of which the component 6 is connectedelectrically to at least one of the conductor pattern layer 14, 19. Inaddition, the circuit-board construction includes at least one thermalvia 22, which is a structural component boosting thermal conduction andextending in the insulating layer 1, which is located in the vicinity ofthe component 6. The actual component can be, for example, an uncasedsemiconductor chip.

In one embodiment, the circuit-board construction includes a thermalvia, or thermal vias on the side of both the first and second surface ofthe insulating-material layer 1. These thermal vias on both sides canalso be manufactured using the same method and even in the same processstage. The circuit-board construction can thus include thermal vias 22,which have the same construction, on both sides of the component 6. Thethermal vias 22 can also have the same construction to the vias made forthe electrical contacts of the component. Like the electrical contacts,the thermal vias can also be manufactured in such a way that they areconnected to the conductor pattern layers 14, 19, so that the conductingof heat away from the vicinity of the component becomes more efficient.

In one embodiment, the thermal via 22 consists of pure, uniform metal.This metal is usually copper and it can be manufactured, for example,using a chemical and/or electrochemical deposition method.

The thermal via 22 can be in contact with the surface of the component6, in which case the conducting of the heat will be efficient. A veryeffective contact will be obtained, if there is a metallurgical contactbetween the via and the component. This will also permit an electricalcontact to be created through the thermal via 22, for example, toconnect the ground potential to the component.

The number, location, and cross-sectional areas of the thermal vias areselected according to the application. Factors to be taken into accountinclude a sufficient thermal conduction capacity and efficient use ofspace, when the available space is divided effectively between theelectrical conductors and the thermal conductors. The methods describedabove permit the thermal vias to be precisely positioned in the desiredareas, as well as a very free choice of the dimensions of the vias.

In the following are descriptions of examples of some possibledimensions of thermal vias. On the surface of the component 6, there areboth contact areas, which are intended for the creation of electricalcontacts, and the surface outside them. In the following, this surfaceoutside the contact areas is referred to as the free surface. Further,for the examination the free surface is defined to include the surfacearea on the first surface of the component and on the second surfaceopposite to this, as well as on the edge surfaces, which connect thefirst and second surfaces to each other. The term first surface thusrefers to the surface of the component, on which most of the contactareas are located. In the circuit-board construction, the thermal vias22 are typically designed on the free surface and, in many embodiments,in such a way that they come into contact with the free surface of thecomponent on the first surface, the second surface, and/or the area ofthe edge surface.

In an embodiment forming such a contact, the common contact surface areaof the thermal via 22 and the component with the second surface can be,for example, at least 50%, when a good thermal conduction capacity willalready be achieved. If a very effective thermal conduction capacity isnecessary, the common contact surface can be at least 70% and preferablyeven at least 90% of the surface area of the second surface.

When examining the free surface of the entire component, it is possible,for example, to aim for a common contact surface area between thethermal vias 22 and the component 6 of at least 15% and preferably atleast 30% of the surface area of the free surface. In embodimentsrequiring a very large thermal conduction capacity, the common contactsurface area can even be more than 60% of the surface area of the freesurface.

As an example of the cross-sectional area of the individual thermal vias22, it can be stated that the cross-sectional area of a thermal viashould preferably be designed to be at least 30 μm², if the spaceavailable in the circuit-board construction will only permit this.

1. A method for manufacturing an electronic module, in which method atleast one component (6) is embedded inside an insulating-material layer(1) and contacts (14) are made to connect the component (6) electricallyto the conductor structures (14, 19) contained in the electronic module,characterized in that at least one thermal via (22) is manufactured inthe insulating-material layer (1) in the vicinity of the component (6).2. A method according to claim 1, in which at least one thermal via ismanufactured to be in contact with the surface of the component.
 3. Amethod according to claim 1, in which there is at least one thermal bumpon the surface of the component and at least one thermal via ismanufactured to be in contact with the thermal bump.
 4. A methodaccording to claim 1, in which at least one thermal via is manufacturedin such a way that insulating material is left between the thermal viaand the surface of the component.
 5. A method according to any of claims1-4, in which at least one thermal via forms an electrical contact withthe component, in order to conduct the ground potential to thecomponent.
 6. A method according to claim 5, in which the combineddiameter of the one or several thermal vias forming an electricalcontact is substantially greater than the diameter required to form anoperating electrical connection with the component.
 7. A methodaccording to any of claims 1-4, in which none of the thermal vias formsan electrical contact with the component.
 8. A method according to anyof claims 1-7, in which the manufacture of contacts to connect thecomponent to the conductor structures of the electronic module includes,as one step, the manufacture of electrical vias using a via technique,and in which method at least one thermal via is also made, using thesame via technique.
 9. A method according to any of claims 1-8, in whichthe component has a first surface and a second surface and in which atleast one thermal via is manufactured to the side of the first surfaceof the component and at least one thermal via to the side of the secondsurface of the component.
 10. A method according to any of claims 1-9,in which the electronic module to be manufactured comprises amulti-layer circuit-board, inside which at least one component isembedded, and in which method a conductor pattern is formed in at leastone conductor layer of the multi-layer circuit-board, in order toconduct heat in the lateral direction of the electronic module.
 11. Amethod according to claim 10, in which the conductor pattern forconducting heat in the lateral direction of the electronic module is indirect contact with at least one thermal via.
 12. A method according toclaim 10 or 11, in which a thermal conductor, which is in direct contactwith the lateral-direction thermal conductor pattern, is manufacturedextending in the vertical direction of the multi-layer circuit-board.13. A method according to any of claims 1-12, in which a conductor layeris taken, a component is taken, which has a contacting surface, on whichthere are contact areas, the component is glued on itscontacting-surface side to the first surface of the conductor layer, aninsulating-material layer, which surrounds the component glued to theconductor layer, is manufactured on the first surface of the conductorlayer, vias to connect the contact areas of the component electricallyto the conductor layer are formed, as is at least one thermal via, andconductor patterns are manufactured from the conductor layer.
 14. Amethod according to claim 13, in which, to create electrical vias,openings are opened in the conductor layer and the adhesive layer at thelocations of the component's contact areas, and, in order to createthermal vias, recesses are formed in the conductor layer and theadhesive layer in the component's surface that is free of contact areas.15. A circuit-board construction, which includes an insulating-materiallayer (1), at least two conductor pattern layers (14, 19), at least onecomponent (6) inside the insulating-material layer (1), and contacts(14) to connect the component (6) electrically to at least one of theconductor pattern layers (14, 19), characterized in that thecircuit-board construction includes at least one thermal via (22) in theinsulating-material layer (1) in the vicinity of the component (6). 16.A circuit-board construction according to claim 15, in which at leastone of the conductor pattern layers (14, 19) is situated on the side ofthe first surface of the insulating-material layer (1) and at least oneother of the conductor pattern layers (14, 19) is situated on the sideof the opposite surface of the insulating-material layer (1), and inwhich at least one thermal via (22) is connected to the conductorpattern layer (14, 19) on the side of the first surface and at least oneother thermal via (22) is connected to the conductor pattern layer (14,19) on the side of the second surface.
 17. A circuit-board constructionaccording to claim 16, in which both the thermal via (22) connected tothe conductor pattern layer (14, 19) on the side of the first surfaceand the thermal via (22) connected to the conductor pattern layer (14,19) on the side of the second surface have a similar construction.
 18. Acircuit-board construction according to any of claims 15-17, in whichthe thermal via (22) consists of pure, uniform metal.
 19. Acircuit-board construction according to any of claims 15-18, in whichthe material of the thermal via (22) is a metal, for example copper,manufactured by a chemical and/or electrochemical deposition method. 20.A circuit-board construction according to any of claims 15-19, in whichthe material of the thermal via (22) is in contact, preferably inmetallurgical contact, with the surface of the component (6).
 21. Acircuit-board construction according to any of claims 15-20, in whichthe construction of the thermal vias (22) is similar to that of thecontacts that connect the electrical contact areas of the component toat least one of the conductor pattern layers (14, 19).
 22. Acircuit-board construction according to any of claims 15-21, in which atleast one thermal via (22) forms an electrical contact with thecomponent, for example, in order to conduct the ground potential to thecomponent.
 23. A circuit-board construction according to any of claims15-22, in which there are contact areas on the surface of the component(6) for the creation of electrical contacts, as well as a free surfaceoutside the contact areas, which free surface includes a surface area onthe first surface of the component and on the second surface opposite tothis, as well as on the edge surfaces that connect the first and secondsurfaces to each other, and in which circuit-board construction at leastone thermal via (22) comes into contact with the free surface of thecomponent.
 24. A circuit-board construction according to claim 23, inwhich at least one thermal via (22) comes into contact with the freesurface, in the area of the edge surface.
 25. A circuit-boardconstruction according to claim 23 or 24, in which at least one thermalvia (22) comes into contact with the free surface, in the area of thefirst surface.
 26. A circuit-board construction according to any ofclaims 23-25, in which at least one thermal via (22) comes into contactwith the free surface, in the area of the second surface.
 27. Acircuit-board construction according to claim 26, in which the combinedcontact surface area of one or more thermal vias (22) with the secondsurface is at least 50 %, preferably at least 70%, and most preferablyat least 90% of the surface area of the second surface.
 28. Acircuit-board construction according to any of claims 23-27, in whichthe common contact surface area between the thermal vias (22) and thecomponent (6) is at least 15%, preferably at least 30%, and mostpreferably at least 60% of the surface area of the free surface.
 29. Acircuit-board construction according to any of claims 15-28, in whichthe cross-sectional area of at least one thermal via (22) is at least 30μm.
 30. A circuit-board construction according to any of claims 15-29,in which the component is an uncased semiconductor chip.